WORCESTER — A judge approved Alberto L. Sierra's transfer to another jail Thursday after being told Mr. Sierra feared for his safety at the Essex County Jail and House of Correction in Middleton.

Mr. Sierra, the boyfriend of Jeremiah Oliver's mother, Elsa Oliver, is being held on $250,000 cash bail on kidnapping, assault, child endangerment, and other charges. Ms. Oliver is also facing similar charges.

The body of 5-year-old Jeremiah, who had been missing since September, was found April 18 by the side of Interstate 190 in Sterling. Police and prosecutors are treating his death as a homicide. No new charges have been filed since the child's remains were discovered.

Alan J. Black, Mr. Sierra's lawyer, filed a motion Thursday in Worcester Superior Court asking that his client be transferred from the Essex County jail to one in Hampden, Franklin or Hampshire County. The motion, unopposed by Assistant District Attorney Cheryl R. Riddle, was approved by Judge David Ricciardone.

Mr. Black said in his motion that Mr. Sierra "believes that his life is in danger at the Essex County Jail and fears for his safety." The alleged victims of the charges lodged against Mr. Sierra include Jeremiah and two of his siblings, as well as Ms. Oliver, who remains in custody on $100,000 cash bail.

Because of the nature of the charges, Mr. Sierra has been held in "solitary confinement" at the Essex County facility, according to Mr. Black's motion, which goes on to say that Mr. Sierra believes he would be allowed to be "out in population" at another jail.

Mr. Black, who is from the Springfield area, also noted that the Middleton jail is about two hours from his office and said it has been "extremely difficult" for him to meet with Mr. Sierra on a regular basis to prepare his defense.